Automatic container handling is typically accomplished by means of a crane having a generally rectangular shaped movable trolley located on a repositionable frame. A generally rectangular shaped spreader is used both to move containers onto a stack located on the ground or on a ship beneath the frame and to pick up target containers from such a stack. Spreader is typically connected to trolley by means of cables for raising and lowering the spreader. Crane operators are often located in a cabin more than 100 feet above the pick-up and drop-off point for the containers. Efficient operations call for relatively fast raising and lowering of the spreader mechanism with the hoist. However, due to the distances involved and the physical positioning of the spreader and container, the operators are frequently unable to personally see the container which they are handling or the target area for the spreader. Consequently, they must rely on either their own visual memory or signals from others located at the pick-up or drop-off point to manually reduce the speed of the spreader mechanism. If the spreader speed is reduced too soon, the operating cycles becomes over-extended, i.e. too much time transpires resulting in inefficient and more costly operation cycles. If the spreader speed is reduced too late, a hard landing may occur causing damage to the spreader, a ship hold or hatch, the crane operating mechanism and/or the target container. Common industry experience indicates that over 50% of container handling crane maintenance costs and down time are due to spreader repair
What is needed, therefore, is a system and method for regulating the speed of a spreader as it is lowered into position to either pick-up or drop-off a container and which is equally functional in the lanes between crane legs, in the back reach.